JP6427465B2 - Method of producing strontium titanate fine particles having cubic shape, cubic shape strontium titanate fine particles, cube shaped metal-doped strontium titanate fine particles, and method of producing the same - Google Patents

Description

A multilayer ceramic capacitor (common name: MLCC (Multiple) that achieves miniaturization and large capacity by multilayering ceramic dielectrics and metal electrodes as one of the electronic components widely used in various electronic devices of today. There is an electronic component called “layer ceramic capacitor)), but the present invention is suitable for constructing a layer in which the conductivity of the dielectric ceramic is improved in order to improve the ohmic characteristics in the vicinity of the electrode layer. The present invention relates to shape-controlled strontium titanate fine particles and rhodium-doped strontium titanate fine particles, and a method for producing the same.
At the same time, according to the present invention, shape-controlled titanic acid as a raw material suitable for constituting a photocatalytic material, which is currently in the limelight as an environmental energy material, by performing decomposition of water into hydrogen or oxygen by visible light. The present invention also relates to strontium fine particles, rhodium-doped strontium titanate fine particles, and a method for producing the same.

Strontium titanate (SrTiO ₃ ) is a composite oxide material that is expected to be developed for various applications as functional materials, such as dielectric properties, thermoelectric properties, photocatalytic ability, high refractive index properties, and photochromic properties. Along with the recent miniaturization of electronic devices, excellent high-capacitance capacitors with less voltage loss have attracted attention, while high-performance photocatalytic activity has attracted attention from the viewpoint of energy problems and environmental problems. Strontium titanate is expected to be a material for forming an electrode interface layer such as a ceramic capacitor from the viewpoint that the band gap can be controlled by metal doping, and from the high stability under light irradiation and the strength of photoreduction power. An expectation is increasing as a base material for a photocatalytic material that enables hydrogen production using sunlight.

With regard to the ohmic contact formation layer at the ceramic capacitor electrode interface, when the work function (φM) of the metal electrode is smaller than the work function (φS) of the semiconductor ceramic, non-rectifying contact, that is, ohmic contact is obtained. The problem of the relative position between the electrode and the Fermi surface of the semiconductor ceramic is that the semiconductor ceramic is doped with an element that modulates the band structure, and this material is used as an intermediate layer between the electrode layer and the semiconductor ceramic layer. It is expected to be able to give sex.
Moreover, as a mother catalyst material directed to the photocatalyst material, it is preferable to have activity to visible light which occupies a large proportion of sunlight. Strontium titanate with metal such as Pt, Rh, Cu supported as co-catalyst as a strontium titanate photocatalyst capable of highly efficient hydrogen generation with visible light activity, and effective use of visible light region of sunlight Strontium titanate etc. which modulated the band structure by doping Rh, Ir etc. for the purpose are expected.

  Among various functional materials, in particular, perovskite-type oxide fine particle (nanoparticles) materials can realize high-performance, small-size, and light-weight products because they can exhibit unique excellent properties and functions. As expected, in particular, particles synthesized via a liquid phase have extremely high uniformity in terms of particle size and composition, so fine particle synthesis technology by liquid phase process, and nano Particleization technology is being considered.

Perovskite-type oxide fine particles are represented as ABO ₃ in the general formula, in the A site, +2 valence elements such as Ca, Sr, Ba, Pb etc. and in the B site +4 valence elements such as Ti, Zr, Sn etc. It is known to enter.
Among these, Patent Document 1 is known as a patent relating to a technique capable of directly synthesizing SrTiO ₃ -based perovskite-type fine particles in an aqueous solution. Although this patent is liquid phase synthesis at atmospheric pressure, cubic shaped fine particles have not been obtained. In particular, Patent Document 1, which describes a production method for directly synthesizing SrTiO ₃ fine particles in an aqueous solution, contains as the optimum synthesis conditions:
The pH value of the aqueous solution is 13.5 or more, the temperature is near the boiling point at atmospheric pressure of 90 ° C. or more,
The reaction time is about 2 hours, and the [Sr] / [Ti] molar ratio at the time of feeding is preferably 1, while the form of the obtained fine particles is as follows:
Only the description “the particle size of the SrTiO ₃ fine particles was uniform at 100 to 200 Å”, and the shape was not described at all.

With respect to shape control of the strontium titanate fine particles, the development of the technology after that is described in Patent Document 2, Patent Document 3, Patent Document 4, Furthermore, Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3 ing.
Patent Document 2 discloses that strontium hydroxide and a water-soluble titanium compound such as ammonium titanium peroxolactate are used in the presence of an amphiphilic compound such as oleic acid and a metal element-free basic compound such as hydrazine at 200 ° C. It is described that by hydrothermal synthesis under alkaline conditions, it is possible to produce strontium titanate nanoparticles with controlled crystal shape without aggregation.

  In addition, Patent Document 3 discloses a method of aligning cube-shaped strontium titanate nanocrystals on a substrate and a method of producing a film composed of nanocrystals, as described in paragraph [Patent Document 3]. In the synthesis of strontium titanate nanocrystals, crystal growth proceeds with molecules of an organic carboxylic acid such as oleic acid adhering to the {100} plane, so crystal growth on the {111} plane is an organic carboxylic acid. The discussion of the particle shape control mechanism is also described, including the progress of the growth of all eight {111} planes to form a vertex as a whole, without being hindered by the acid molecules to form a vertex as a whole.

Further, in Patent Document 4, the same perovskite type BaTiO ₃ or SrTiO _{3 is} subjected to hydrothermal synthesis conditions up to 150 ° C. for 120 hours, and for SrTiO ₃ , formation of cubic-shaped particles is an electron microscope It has been reported through observation. However, it is not a synthesis case under atmospheric pressure, and there is no description of a metal element-doped system.

In addition, in Non-Patent Document 1 and Non-Patent Document 2, in addition to the fact that cube-shaped SrTiO ₃ fine particles are obtained by performing hydrothermal synthesis at 240 ° C. for 24 hours in a highly alkaline solution, evaluation by Raman scattering In addition, the technology of putting Pt on the surface of the diced SrTiO ₃ particles by atomic layer deposition (ALD) method is introduced. Pt clearly has a meaning as a cocatalyst for photocatalysts. However, both reports do not mention metal doping at all.

On the other hand, in Non-Patent Document 3, after strontium hydroxide and titanium dioxide are mixed in ethanol in a nitrogen atmosphere, an annealing process is performed in a temperature range of 800 ° C. to 1000 ° C. after hydrothermal synthesis at 170 ° C. for 3 days. It has been reported that preparation of a cubic light-responsive Rh-doped strontium titanate fine particle is carried out. The doping amount is 1%, and no discussion has been made from the viewpoint of how much doping is possible. Furthermore, there is no description of crystal lattice constant etc., and it is judged that it is doped from the optical absorption spectrum. The important point here is that the morphology of the non-doped SrTiO ₃ fine particle immediately after hydrothermal synthesis is described as a cubic shape in an electron micrograph (SEM photo), while the SEM photo is not clearly shown but only in the text. “The particle shape of hydrothermally synthesized 1% Rh-doped SrTiO ₃ does not affect the non-doped cubic shape by doping”. Thus, in this document, the description of the morphology and crystallinity of the fine particles immediately after hydrothermal synthesis is hardly described, and high temperature heat treatment at 800 ° C. to 1000 ° C. is performed immediately after hydrothermal synthesis, and the final Since the evaluation of the material is evaluated at that time, it can be said that it is unclear how much the doping condition is realized only by hydrothermal synthesis. Further, it is added that Non-Patent Document 3 also reports doping of Ru, Ir, Pt, and Pd in addition to Rh.

The situation up to this point is shown in Table 1 on the next page.
Rh-doped SrTiO ₃ fine particles whose shape is cubic and whose synthesis method is based on liquid phase synthesis under atmospheric pressure which does not require high temperature and high pressure are present in conventional published documents. Not.
On the other hand, there are no reported cases of the preparation method of atmospheric pressure liquid phase synthesis of non-doped pure SrTiO ₃ cubic shaped fine particles in the published documents up to now.

  Here, the research purpose of the above Non-Patent Document 3 describing Rh doping is based on the improvement of the photocatalytic ability by doping metallic elements such as Rh and iridium (Ir) to strontium titanate. is there. Specifically, there are Rh-doped or Ir-doped strontium titanate fine particles having high photocatalytic activity described in Patent Document 5. This patent document 5 is an invention of a Rh-doped SrTiO3 photocatalyst material, and shows that the efficiency is highest when 1% Rh is doped in the range of 3% Rh doping. Among them, the sample preparation method is a typical ceramic solid phase reaction method, and it is calcined at 1150 ° C. for 10 hours after calcination at 1000 ° C. for 1 hour. Patent Document 5 does not touch on liquid phase synthesis such as hydrothermal synthesis at all.

The doping amount of Rh synthesized as a single phase is less than 7%. (4% is proved to be single phase by X-ray diffraction.) This single phase data of less than 7% of Rh is based on solid phase reaction method and is not finding by liquid phase method or hydrothermal synthesis method . Under these circumstances, there have been no reports in the literature that so far have reported single-phase Rh-doped SrTiO ₃ particles by liquid phase synthesis under hydrothermal conditions or hydrothermal synthesis. .

Further, the background that the present inventors place importance on the particle form of cube shape is not only the convenience for controlling the orientation and arranging of the particles but also the idea of effectively utilizing the active surface as a photocatalyst. The active surface of SrTiO ₃ photocatalytic material is shown to be {100} from Non-Patent Document 4 here, and if such shape control is performed at the time of fine particle synthesis, it is a great progress in future photocatalyst technology. We believe that is expected.

Japanese Examined Patent Publication 3-39016 JP 2011-68500 A) Patent No. 5618087 Public Relations Patent No. 5216186 gazette Patent No. 4076793

F. A. Rabuffetti et al., Chem. Mater., 20 (2008) 5628-5635. S. T. Christensen et al., Small, 5 (2009) 750-757. S. W. Bae et al, Applied Physics Lett. 2008, 92, 104107. Jennifer L. Giocondi et al., Topics in Catalysis, 44 (2007) 529-533.

The prior art from the viewpoint of directly synthesizing crystalline strontium titanate (SrTiO ₃ ) fine particles in a liquid phase which can obtain highly homogeneous fine particles and which can be controlled to a specific shape such as a cubic shape. If any of Patent Document 2, Patent Document 3, Patent Document 4, Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3 synthesizes fine particles under the conditions of hydrothermal synthesis requiring high temperature and high pressure. doing. Although each of these patent documents clearly indicates that the form of the obtained fine particles is cubic, in any case, it is a chemical reaction under high temperature and high pressure, and has a relatively long time, etc. There are major barriers to industrialization in terms of productivity and capital investment in mass synthesis. Moreover, although the description regarding Rh dope is only these nonpatent literature 3 in these patent documents and nonpatent literatures, as it mentioned above, since high temperature annealing treatment is given immediately after hydrothermal treatment, the particles after hydrothermal treatment The nature of the substance is often unclear.

On the other hand, although patent document 1 is reported as a liquid phase manufacturing method of strontium titanate microparticles under atmospheric pressure, there is neither description nor suggestion about the method of shape control to the cube shape which has a specific crystal face. In addition, there is no description at all regarding doping of metal elements such as Rh.
In view of these circumstances, it can be concluded that there is no prior report that cubic strontium titanate (SrTiO ₃ ) fine particles were synthesized in the liquid phase synthesis process under atmospheric pressure. As a matter of course, there is no prior case where metal-doped cubic SrTiO ₃ fine particles were synthesized in a liquid phase process under atmospheric pressure, in the literature reported so far.

  By the way, although the case of Rh-doped hydrothermal synthesis is only described in Non-Patent Document 3, the doped Rh concentration is about 1%, and as the synthesis process, hydrothermal synthesis is performed in the first stage process. It is not easy to guess from this paper alone how much Rh-doped SrTiO3 fine particles could be synthesized only by the hydrothermal treatment, since heat treatment is carried out in the second step process. Anyway, it is not suitable for the production at cost reduction instead of synthesis under atmospheric pressure, in that the hydrothermal reaction under high temperature and high pressure is used.

  The present invention has been made in view of the above-mentioned circumstances, and produces strontium titanate fine particles or Rh-doped strontium titanate fine particles whose shape is controlled in a cubic shape having a specific crystal plane with good productivity under atmospheric pressure. The purpose is to

The method for producing strontium titanate fine particles having a cubic shape of the present invention is
A reaction liquid preparation step of preparing a reaction liquid in which a strontium raw material and a titanium raw material are added to an alkaline aqueous solution;
And a reaction step of heating the reaction solution to 80 ° C. or higher under atmospheric pressure to cause the reaction solution to react.

  In the present specification, “strontium titanate fine particles” include non-doped strontium titanate fine particles and metal-doped strontium titanate fine particles, unless otherwise specified.

  As used herein, "reacting the reaction solution" means reacting one or more components contained in the reaction solution.

  Further, in the present specification, the term "fine particles" means particles having an average particle size of less than 1 μm, preferably nanoparticles. Nanoparticles may generally refer to those having an average particle size of 200 nm or less, preferably 200 nm or less. In some cases, the nanoparticles may be of a size with an average particle size of 100 nm or less, and in other cases with a size of 50 nm or less. Also preferably, the nanoparticles are of a size whose average particle size is less than or equal to 20 nm, and in other cases they are of a size which is less than or equal to 10 nm or less than or equal to 5 nm Good. In addition, in a preferred case, the particle size of the nanoparticles is preferably uniform, but in some cases, it may be preferable to mix particles having different particle sizes at a certain ratio.

The measurement of the average particle size can be carried out by methods known in the art. For example, transmission electron microscopy (TEM), adsorption method, light scattering method, X-ray small angle scattering method (SAXS: It can be measured by Small Angle X-ray Scattering etc. In TEM, observation is performed with an electron microscope, but when the particle size distribution is wide, it is necessary to pay attention to whether or not the particles within the field of view represent all particles. The adsorption method is to evaluate the BET surface area (surface area value of the material based on the theory in which the three members of Brunauer, Emmett, Teller are the monolayer adsorption theory Langmuir theory extended to the multilayer layer) by N ₂ adsorption etc. is there.

In the method for producing strontium titanate fine particles of the present invention, the titanium raw material preferably contains titanium oxide, more preferably titanium dioxide, and the main component of titanium dioxide is anatase type titanium dioxide preferable. Here, the main component means a component having a content of 70% by mass or more.
The strontium raw material preferably contains at least one of an acetate, a nitrate, a chloride, a carbonate, a sulfide, and a hydroxide of strontium.

In the present specification, “titanium oxide” means TiO ₂ which is a stoichiometric composition, and titanium dioxide having a stoichiometric composition represented by TiO _x (1.5 ≦ x ≦ 2), and oxygen The oxide group of the Magneli phase with defects is meant. In addition, the titanium oxide may be a hydroxide such as Ti (OH) ₄ or TiO ₂ · nH ₂ O (0 <n <2) or a hydrate in an aqueous solution.

The temperature at which the reaction solution is reacted in the reaction step is preferably 90 ° C. or more and the boiling point or less under atmospheric pressure, and more preferably in the vicinity of the boiling point if possible. “Boiling point” naturally means the boiling point of the reaction solution to be reacted.
In the reaction step, the pH of the reaction solution is preferably 13.5 or more.

  In the reaction liquid preparation step, Rh (rhodium) can be contained in the alkaline aqueous solution in addition to strontium (Sr) and titanium (Ti), whereby Rh-doped strontium titanate fine particles can be produced. Furthermore, part of the Rh is converted to V (vanadium), Cr (chromium), Mn (manganese), Fe (iron), Co (cobalt), Ni (nickel), Cu (copper), Zn (zinc), Ga Gallium), Nb (niobium), Mo (molybdenum), Ru (ruthenium), Pd (palladium), In (indium), Sb (antimony), Ta (tantalum), W (tungsten), Re (rhenium), Ir (ir) It is also possible to substitute with at least one or more metal starting materials of iridium), Pt (platinum / platinum), Bi (bismuth) or (La (lanthanum), and strontium titanate fine particles doped with these metals can be used. Preferably, at least Rh is present as the metal to be doped, and the metal source is a water-soluble source Preferred.

  The total molar ratio of the metal source to be doped to the strontium source in the reaction solution is preferably 0.15 or less. The total molar ratio of the metal material to the strontium material means the ratio to the molar concentration of the sum of the respective metal elements. For example, the molar ratio of rhodium chloride to strontium hydroxide is expressed as [Rh] / [Sr] which is the ratio of rhodium molar concentration [Rh] to strontium molar concentration [Sr] in the reaction solution. When a part of rhodium is substituted by one kind of metal element M, it means [Rh] + [M] / [Sr].

The cubic strontium titanate fine particles of the present invention are produced by the method for producing strontium titanate fine particles of the present invention.
Further, the cube-shaped rhodium-doped strontium titanate fine particles of the present invention are
Formula _{Sr (Ti 1-x (Rh} 1-y, M y) x) is represented by _{O 3,}
0 <x ≦ 0.07 and 0 ≦ y <1, M is V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Nb, Mo, Ru, Pd, In, Sb, It is at least one metal element selected from the group consisting of Ta, W, Re, Ir, Pt, Bi, and La.

In the present specification, “strontium titanate fine particles having a cubic shape (cube shape) and rhodium-doped strontium titanate fine particles” refer to strontium titanate fine particles and rhodium-doped strontium titanate having a shape in which a part of the apex is chamfered. It also contains fine particles. The strontium titanate fine particles and the rhodium-doped strontium titanate fine particles of the present invention are substantially cube-shaped, and in a transmission electron microscope (TEM) image, a rectangular outer circumscribing such that the area is minimized for one isolated particle. When the rectangular area S ₀ and the area S _{cube of the} particle image are used, the particles satisfy 0.8 <S _cube / S ₀ . Strontium titanate fine particles and rhodium-doped strontium titanate fine particles have a crystal structure in which cubic crystals are stable at room temperature, so the shape of the ideal fine particles is cubic, but cubic strontium titanate fine particles and rhodium-doped titanium It is assumed that hexahedral-shaped microparticles within the range considered to be in the form of strontium strontium microparticles are substantially cube-shaped.

  In such strontium titanate fine particles and rhodium-doped strontium titanate fine particles, 85% or more of the crystal plane exposed on the particle surface is preferably a {100} plane. The length of one side of the cubic particle is preferably 10 nm or more and 500 nm or less.

In the cube-shaped rhodium-doped strontium titanate fine particles of the present invention, the lattice constant value is preferably in the range of 0.3915 nm or more and 0.3930 nm or less. Further, the optical band gap is preferably in the range of 3.21 eV or more and 3.54 eV or less.
It is preferable that the cube-shaped rhodium-doped strontium titanate fine particles of the present invention have a cube shape in which the average value of the length of one side is 30 nm or more and 80 nm or less.
In the present specification, with the average value of the length of one side (average particle diameter), arbitrary 10 particles having a cubic shape are selected from a TEM photograph with a magnification of 100,000, and the length of one side of each particle It is the average value which measured (particle diameter).

  The method for producing strontium titanate fine particles according to the present invention comprises a reaction liquid preparation step of preparing a reaction liquid in which a strontium raw material and a titanium raw material are added to an alkaline aqueous solution, and the prepared reaction liquid at 80 ° C. or higher under atmospheric pressure. And a reaction step of reacting the reaction solution. According to this configuration, strontium titanate fine particles or Rh-doped strontium titanate fine particles whose shape has been controlled to a cubic shape having a {100} plane by preferentially growing <111> crystal orientation of strontium titanate crystals Can be produced at atmospheric pressure with good productivity.

The flow figure of the manufacturing method of the strontium titanate particles of the present invention. The figure which shows the relationship between the titanium dioxide phase as a starting material, the shape (transmission electron micrograph, TEM photograph) of a strontium titanate fine particle obtained, and a X-ray-diffraction pattern. The figure which showed the X-ray-diffraction pattern of the microparticles | fine-particles obtained in each step of the manufacturing process sequentially (Example 3). The TEM photograph which showed the morphological change of microparticles | fine-particles by the reaction time of synthesis | combination (Example 3). The figure which showed the relationship between Rh dope amount and a X-ray-diffraction pattern (Example 4). FIG. 16 shows the relationship between the Rh doping amount and the lattice constant in Example 4. The TEM photograph (low magnification) which shows the relationship between the amount of Rh doping and the form of fine particles (Example 4). The TEM photograph (high magnification) which shows the relationship between the amount of Rh doping and the form of fine particles (Example 4). The figure which shows a nano beam limited field-of-view electron diffraction pattern (Example 4). The figure which shows the result of having measured the diffuse reflection spectrum of each sample of Example 4. FIG. The figure which shows the relationship between Rh dope amount and an optical band gap. The figure which shows the electron spin resonance signal (ESR signal) derived from Rh 4 valence (Example 4). The figure which shows the ESR signal derived from Rh4 valence (solid phase method). The figure which shows the thermogravimetric-mass spectrometry result of Rh dope strontium titanate microparticles | fine-particles (Example 3). The figure which shows the synthetic | combination possible area | region of cube-shaped Rh-doped strontium titanate microparticles | fine-particles.

"Production method of strontium titanate fine particles"
With reference to the drawings, a method of manufacturing strontium titanate particles according to an embodiment of the present invention will be described. FIG. 1 shows a flow diagram of the method for producing strontium titanate fine particles of the present embodiment.

  As described above, although there have been some reports on the production of cubic shape-controlled strontium titanate fine particles having a specific crystal face, all of them are by hydrothermal synthesis under high pressure, It has not been studied at all under atmospheric pressure.

This means that even in simple oxides such as cerium dioxide (CeO ₂ ) and titanium dioxide (TiO ₂ ), shape controllability tends to be increased by making the reaction field a supercritical condition, ie, high temperature and high pressure conditions. Because the crystal structure of the strontium titanate fine particle is complicated, the shape control condition of the complex is considered to be stricter than that of the simple oxide.

  The present inventors diligently studied the mechanism of shape control of strontium titanate fine particles. The case of simple oxide fine particles whose shape is controlled under supercritical conditions can be seen when the water in the reaction solution exceeds the critical point, the solubility of the material drops sharply, and the formation of crystal nuclei and their growth rapidly In order to proceed, that is, because the number of particles generated increased, in order to achieve shape control in low temperature synthesis under atmospheric pressure, it was thought that another device or device was necessary. In fact, in the production of strontium titanate fine particles, it was also confirmed that the shape controllability was deteriorated only by changing the reaction site from hydrothermal conditions to supercritical conditions.

Therefore, the present inventors conducted investigations focusing on the states of the titanium source and the strontium source in the reaction liquid as conditions important for shape control.
The present inventors focused on the potential-pH diagram of Ti in an aqueous solution, and titanium raw materials used in conventional hydrothermal synthesis were titanium dioxide hydrate (TiO ₂ · H _{2) in} an aqueous solution according to pH conditions and the like. It was thought that the change in bonding state such as O), Ti hydroxide (Ti (OH) ₄ ) or HTiO ₃ ^- ion state influences the shape control of the strontium titanate fine particles.
In the conventional method, when the hydrogen ion concentration condition comparable to pH 13.5 or more is used, the shape controllability is good, and therefore, Ti hydroxide (Ti hydroxide stable in the reaction liquid under strong alkaline conditions) (OH) ₄ ) or HTiO ₃ ⁻ ions are stably formed in the reaction solution, that is, by using titanium oxide as a titanium raw material added to water in preparation of the reaction solution, atmospheric pressure It has been found that even shape-controlled strontium titanate fine particles can be produced.

That is, in the method for producing strontium titanate fine particles of the present invention,
A reaction liquid preparation step of preparing a reaction liquid in which a strontium raw material and a titanium raw material, particularly a titanium oxide raw material are added to an alkaline aqueous solution;
The reaction solution is heated at 80 ° C. or higher under atmospheric pressure to react the reaction solution.

  In the reaction liquid preparation step, a reaction liquid in which a strontium (Sr) raw material and a titanium (Ti) raw material are added to an alkaline aqueous solution is prepared. If the reaction liquid can be prepared, the order of mixing the Sr raw material, the Ti raw material, and the compound (hereinafter referred to as a basic compound) for making the aqueous solution alkaline is not particularly limited. It is preferable to add an aqueous solution of a basic compound after mixing them after preparing each of In the reaction liquid preparation step, the aqueous solution prepared after the end of the step is the reaction liquid, but in the present specification, in the explanation of the reaction liquid preparation step, the mixed liquid in the process of preparation is described as the reaction liquid for convenience. Sometimes.

  The method of mixing these aqueous solutions is not particularly limited, but from the viewpoint of minimizing the formation of precipitates in the mixing process, it is preferable to well stir during preparation of the reaction solution. In addition, it is more preferable to carry out the stirring until immediately before carrying out the reaction step of the next step.

  The Ti raw material is not particularly limited as long as it is a Ti oxide, but titanium dioxide is preferable. Although titanium dioxide is mainly anatase type and rutile type, it is preferably anatase type because it has a skeleton relatively close to the perovskite type skeleton. Therefore, it is most preferable to contain anatase type titanium dioxide as a main component as the Ti raw material. As the Ti raw material, it is preferable to use a Ti-containing aqueous solution in which a titanium oxide is dissolved in water.

  The concentration of Ti oxide can be arbitrarily selected according to the concentration to be obtained, but from the viewpoint of obtaining shape-controlled strontium titanate fine particles with good uniformity and productivity, 1 mmol / L or more and 500 mmol / l. It is preferable that it is L or less.

  The Sr raw material is not particularly limited, but a water-soluble Sr compound is preferable. Specifically, Sr hydroxides, oxides, chlorides, fluorides, halides such as iodides, nitrates, carbonates, inorganic acid salts such as sulfates, acetates, oxalates, lactates, etc. And the like, and preferably contain at least one of acetate, nitrate, chloride, sulfide, and hydroxide. As a Sr raw material, it is preferable to use the Sr containing aqueous solution which melt | dissolved the said Sr compound in water.

  The pH of the reaction solution is not particularly limited as long as it is alkaline, but it is preferably a strong alkaline condition of pH 13 or more. Adjustment of the pH can be carried out by adding a basic compound such as potassium hydroxide or sodium hydroxide having an ionization degree of 0.8 or more to the reaction solution. When such a basic compound is used, the concentration of the basic compound in the reaction solution is preferably 1 mol / L or more. The basic compound is preferably made into an aqueous solution (alkaline aqueous solution) and dropped into the reaction solution under preparation.

  In the reaction liquid preparation step, Rh (rhodium), or a part of the Rh in the alkaline aqueous solution in the reaction liquid, V (vanadium), Cr (chromium), Mn (manganese), Fe (iron), Co (cobalt), Ni (nickel), Cu (copper), Zn (zinc), Ga (gallium), Nb (niobium), Mo (molybdenum), Ru (ruthenium), Pd (palladium), In (indium), At least one metal raw material of Sb (antimony), Ta (tantalum), W (tungsten), Re (rhenium), Ir (iridium), Pt (platinum / platinum), Bi (bismuth) or La (lanthanum) Strontium titanate fine particles doped with these metals can be manufactured by including the metal raw material substituted by. From the viewpoint of mixing in an alkaline aqueous solution, the metal source is preferably a water-soluble source. Examples of water-soluble metal raw materials include chlorides, oxides, and nitrates of the above metals.

  Among the metal elements exemplified above, the addition of the Rh element or one in which a part of the Rh element is substituted by another element can significantly increase the visible light responsiveness of the obtained oxide particles. In addition, since the band gap can be adjusted and controlled, the capacitor characteristics can be improved by changing the potential barrier with the electrode. As preferable rhodium raw materials, rhodium (III) chloride, rhodium (III) oxide, rhodium (IV) oxide, rhodium (III) nitrate and the like can be mentioned.

  From the viewpoint of obtaining high photocatalytic ability, it is preferable that the addition amount of the metal raw material be as large as possible within the range in which the perovskite structure can be taken. From this point of view, the total molar ratio of the metal source to the Sr source in the reaction solution is preferably 0.001 or more and 0.15 or less. The total molar ratio of the metal source to the Sr source means the ratio of ([Rh] + [M]) / [Sr]. It is preferable to prepare an aqueous solution of the metal source in advance because the metal source is a small amount relative to the strontium source.

  When a metal source is added, the addition of the alkaline aqueous solution may be after the addition of the metal source.

<Reaction process>
In the reaction step, the reaction liquid prepared in the reaction liquid preparation step is reacted at 80 ° C. or higher under atmospheric pressure. The temperature for reacting the reaction solution may be 80 ° C. or more and the boiling point or less, and is preferably 90 ° C. or more.
The synthesis reaction tank used in the reaction step is not particularly limited as long as it can maintain atmospheric pressure, and a round bottom flask is preferable.

  The heating method of the reaction solution is not particularly limited, and can be selected from aluminum block heating, hot plate heating, electric furnace heating, infrared heating, microwave heating and the like. The temperature of the heating device is preferably higher than the boiling point 100 ° C. of water at normal pressure from the viewpoint of heat conduction. The temperature elevation rate is preferably 1 ° C./min to 100 ° C./min from the viewpoint of productivity, but this is not a main factor of the synthesis reaction, so this temperature elevation rate is not limited.

  During the reaction process, the reaction solution is preferably stirred. The stirring speed may be such that the solute is uniformly dispersed, and about 100 rpm to about 1000 rpm is preferable.

  The reaction time is preferably short within the range in which the reaction proceeds sufficiently, but is preferably 2 hours or more and 12 hours or less. Here 12 hours or less is a cost-conscious view.

After completion of the reaction, the reaction solution is preferably subjected to a desalting step to remove alkali components and the like in the solvent. The desalting step is not particularly limited, but a method of separating fine particles synthesized with a solvent by centrifugation or the like is preferable. Preferred conditions for centrifugation include 5000 to 20000 rpm, 5 minutes to 15 minutes, 3 ° C. to 30 ° C. It is preferable to repeat the centrifugation operation twice or more, and between the centrifugation operations, after discarding the supernatant, include a step of adding 20 mL to 100 mL of pure water to obtain a suspension of the synthesized microparticles again. preferable.
On the other hand, after the reaction, decantation is performed several times on the reaction solution to make the pH of the whole solution neutral, and it is also possible to recover fine particles by simple filtration.

  The strontium titanate fine particles obtained after desalting are preferably subjected to the following drying step. The drying step is not particularly limited as long as the moisture of the separated fine particles can be completely evaporated, but it is preferable to dry at 100 ° C. to 120 ° C. for 1 hour to 3 hours. In the drying step, the method of heat treatment is not particularly limited, and can be selected from hot plate heating, electric furnace heating, infrared heating, microwave heating and the like. Although the atmosphere for drying is not particularly limited, it is preferable to carry out under atmospheric pressure and in the air from the viewpoint of production cost and the like.

  As shown in Examples described later, the strontium titanate fine particles obtained by the above method are controlled in shape so that the surface has a {100} plane, and have a cubic shape. Since the strontium titanate fine particles have a crystal structure in which cubic crystals are stable at normal temperature, the surface of the strontium titanate fine particles having a cubic shape has a {100} plane.

  FIG. 13 of the Example described later maps the reaction temperature on the vertical axis and the [Rh] / [Sr] value in the reaction liquid on the production availability of shape-controlled rhodium-containing strontium titanate. FIG. 13 shows strontium titanate fine particles having a cubic or rectangular parallelepiped shape and rhodium doping in the method of the present invention for producing strontium titanate fine particles at a temperature significantly lower than 100 ° C. as compared with the conventional method. It has been shown that strontium titanate microparticles can be produced.

  The method for producing strontium titanate fine particles according to the present invention comprises a reaction liquid preparation step of preparing a reaction liquid in which an Sr raw material and a Ti raw material are added to an alkaline aqueous solution, and the prepared reaction liquid at 80 ° C. or higher under atmospheric pressure. And a reaction step of reacting the reaction solution. According to this configuration, strontium titanate fine particles whose shape has been controlled so that the surface has a {100} plane can be grown preferentially at <110> crystal orientation of the strontium titanate crystal under atmospheric pressure, It can be manufactured with good productivity. The method for producing strontium titanate fine particles of the present invention can be easily synthesized in a large amount by the flow method because it can be synthesized under atmospheric pressure.

"Cube-shaped strontium titanate particles, cube-shaped rhodium-doped strontium titanate particles"
The cubic strontium titanate fine particles of the present invention are produced by the method for producing the strontium titanate fine particles having the cubic shape of the present invention described above, and have a cubic shape.
Further, the cube-shaped rhodium-doped strontium titanate fine particles of the present invention are
Formula _{Sr (Ti 1-x (Rh} 1-y, M y) x) is represented by _{O 3,}
0 <x ≦ 0.07 and 0 ≦ y <1, M is V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Nb, Mo, Ru, Pd, In, Sb, It is at least one metal element selected from the group consisting of Ta, W, Re, Ir, Pt, Bi, and La.
It is preferable that it is Rh single dope strontium titanate microparticles | fine-particles whose y is 0 in the said General formula.

  In such strontium titanate fine particles and rhodium-doped strontium titanate fine particles, 85% or more of the crystal plane exposed on the surface of the cube or rectangular parallelepiped is preferably a {100} plane. Further, the average value of the length of one side of the cube is preferably 10 nm or more and 500 nm or less, and more preferably 30 nm or more and 80 nm or less.

  The application of the fine particles obtained by the method for producing strontium titanate fine particles having a cubic shape according to the present invention is not particularly limited, but the Rh element or a part of the Rh element can be selected from V, Cr, Mn, Fe, Co , Ni, Cu, Zn, Ga, Nb, Mo, Ru, Pd, In, Sb, Ta, W, Re, Ir, Pt, Bi, or another metal element substituted by at least one metal source of La In addition to being able to significantly increase the visible light responsivity of the resulting oxide particles by doping the ones substituted with y, it is possible to adjust and control the band gap, so that the potential barrier with the electrode can be changed. Thus, the capacitor characteristics can be improved. Since fine particles whose shape is controlled in a cubic shape are suitable as catalysts having a large contribution of surface area and plane orientation, they are suitable as raw materials for photocatalysts with very high catalytic performance and raw materials for capacitors suitable for hydrogen / oxygen generation photocatalyst systems. It can be used preferably.

A hydrogen generation photocatalyst system and an oxygen generation photocatalyst system (hereinafter sometimes abbreviated as hydrogen and oxygen photocatalyst system) are photocatalysts that generate hydrogen and oxygen by irradiation of sunlight, and the photocatalyst has a surface area or plane orientation. It is known that the contribution is large. According to the manufacturing method of the cube-shaped rhodium-doped strontium titanate fine particles of the present invention, for example, as shown in FIG. 9, since the control of the band gap by Rh doping can be made clear, the light in the visible range of sunlight It has been shown for the first time that it can be used effectively. At the same time, the controllability of the contact resistance in the vicinity of the electrode is very likely to be improved.
On the other hand, since it is possible to produce uniform cubic shaped fine particles of about 50 nm in which the {100} plane is exposed, which is considered to be the active surface of photocatalyst from Non-Patent Document 4, it is suitable for photocatalyst application.

  The mode for use in the hydrogen / oxygen generation photocatalyst system is not particularly limited, and examples thereof include a mode for a thin film for hydrogen production formed by applying metal-doped strontium titanate fine particles to a substrate.

  In the application of the photocatalyst, the metal-doped strontium titanate fine particles are preferably provided on the surface of the fine particles together with the cocatalyst. Strontium titanate fine particles supporting a metal promoter suppress electron recombination with holes because electrons excited in the strontium titanate by light irradiation move rapidly to the surface due to the presence of the metal promoter on the surface. Thus, hydrogen can be efficiently generated to enable highly efficient reduction reaction.

  When a cocatalyst is added, the addition method is not particularly limited, and examples thereof include a method using an optical electrodeposition method, an impregnation method, electroless plating and the like. From the viewpoint of obtaining a higher photocatalyst and the viewpoint of carrying out the photocatalytic activity evaluation simultaneously with the addition of a cocatalyst, a method using a photo electrodeposition method is preferable.

  As a light source for photo electrodeposition, a xenon lamp, a mercury lamp or sunlight having a distribution with energy higher than the absorption wavelength of oxide particles can be mentioned, but from the viewpoint of performing irradiation with a large area uniformly and inexpensive equipment. A xenon lamp is preferred. In the photo electrodeposition step, it is preferable to irradiate the surface of the reaction vessel with visible light having a wavelength of 420 nm or more at an illuminance.

The atmosphere in the photo-electrodeposition step is not limited, and may be under atmospheric pressure or in any gas, but when evaluating the photocatalytic activity simultaneously, it is preferable to carry out under an argon atmosphere.
The maximum temperature reached of the reaction liquid in the photo-electrodeposition step is preferably 40 ° C. or less, more preferably 10 ° C. to 25 ° C. in order to suppress evaporation of the solvent.

  As the metal promoter, any of platinum, silver, gold, rhodium, chromium and the like is preferable, and any of platinum and rhodium exhibiting high photocatalytic activity is more preferable. For example, as a platinum raw material, it is preferable to use either hexachloroplatinic acid hexahydrate or tetrachloroplatinic acid hexahydrate from the viewpoint of adhering to strontium titanate fine particles by a reduction reaction in a solvent. The concentration of platinum is preferably 0.1% by weight to 20.0% by weight with respect to the weight of strontium titanate.

When an electron trap is generated between the supported metal promoter and strontium titanate which is a mother catalyst (interface), it is difficult for the promoter to fully exhibit its effect. In order to make the electron trap difficult to occur, it is preferable that the strontium titanate fine particles have a crystal face that is as lattice-matched as possible with the supported metal. The lattice constant of cubic strontium titanate whose shape is controlled as described above is about 0.392 nm. The lattice constant of this lattice constant and the lattice constant of the supported metal, Pt, Ir, Pd, Rh, Ru, Cu, Ni, Co, has a mismatch rate of 12% or less, Ir or Pd is 5% or less, Pt is 0 .5% or less, by forming cubic strontium titanate fine particles having a high {100} surface ratio of the surface, a highly efficient photocatalyst with few electron traps at the interface with the supported metal can be realized.
Therefore, it is preferable that the lattice constant value of the cube-shaped rhodium-doped strontium titanate fine particle of the present invention is in the range of 0.3915 nm to 0.3930 nm.

  The rhodium-doped strontium titanate fine particles obtained by the present invention can be used in applications other than hydrogen and oxygen generation photocatalyst systems. For example, by using an organic substance such as a ruthenium complex as a cocatalyst, it is possible to incorporate it into an artificial photosynthesis device that generates an organic substance from carbon dioxide. Furthermore, the combination with an oxygen generation photocatalyst enables complete decomposition of water, and is suitable for a photocatalyst device that simultaneously produces hydrogen and oxygen. The oxygen generation photocatalyst can be suitably combined with tungsten oxide, bismuth vanadate or the like.

  Furthermore, the cubic strontium titanate fine particles have various advantages such as cubic shape being the original shape of cubic crystal particles, easy arrangement, easy formation of a dense film, and the like other than photocatalyst application. Have.

"Design changes"
The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the scope of the present invention.

Examples are described below, but the present invention is not limited by these examples.
Example 1
According to the flow shown in FIG. 1, 1 mol of sodium hydroxide (NaOH) is dissolved in 160 mL of pure water put in a three-necked Teflon (registered trademark) solution to prepare a sodium hydroxide aqueous solution, and strontium nitrate (II) anhydride ( Sr, Ti obtained by adding 2.04 mmol of Wako Pure Chemical Industries, 98%) and 2.04 mmol of titanium oxide (TiO ₂ (P 25)) (Degussa, 99.5%) into 40 mL of pure water The containing aqueous solution was mixed with an aqueous sodium hydroxide solution to obtain a mixed solution. To this mixed solution, rhodium trihydrate _(RhCl 2 · _3H 2 O) chloride (produced by Wako Pure Chemical Industries, Ltd., 95%), and 1.0% of Rh molar concentration in the reaction solution is Sr molar concentration ([Rh] After adding so that / [Sr] = 0.01), a reaction liquid in a suspended state was obtained by irradiating ultrasonic waves for several minutes. The pH of the reaction solution was 14.3.

  The three-necked flask was placed in a thermostatted aluminum block bath (Synflex, BBS-108RB), heated at a stirring speed of 500 rpm for heating and boiling under stirring, and after boiling, refluxed for 6 hours to react the reaction liquid . The set temperature of the thermostatic bath at the time of heating was 150.degree. The temperature of the reaction liquid at boiling was 100 ° C.

In the desalting step, first, the reaction product is divided into five 40 mL aliquots of centrifugation tubes, each of which is subjected to a washing step by centrifugation, and after discarding the supernatant of the centrifugation tube, 20 mL of pure water is added. The turbid solution was subjected to ultrasonication, and the above-mentioned washing step was carried out again. The centrifugation conditions in the washing step were 10 minutes at 10,000 rpm.
After desalting, 30 mL of pure water is added to each of the precipitate-containing centrifuge tubes to obtain a suspension in which the precipitates are dispersed. The resulting suspension is transferred to a petri dish, and the petri dish is placed on a hot plate. The mixture was placed and dried at 100 ° C. for 1 hour to obtain a desalted precipitate.

(Example 2)
Rhodium-doped strontium titanate fine particles were produced in the same manner as in Example 1 except that the titanium raw material was changed to rutile type.

  The results of measuring the TEM photograph and the XRD pattern of the rhodium-doped strontium titanate fine particles obtained in Example 1 and Example 2 are shown in FIG. In FIG. 2, the results of Example 1 are shown as anatase, and the results of Example 2 are shown as rutile. When the titanium raw material was rutile type, there were few particles of cubic shape, and many other phases other than the perovskite phase were observed.

(Example 3)
In this example, under the same production conditions as Example 1, 4 mL each of the reaction solution in the flask was sampled before heating, immediately after boiling, and every one hour after boiling to confirm the time-series change of the product. Each reaction solution is subjected to a desalting step and a drying step to remove alkali components and the like in the solvent, and the precipitate in each sample is recovered, and the XRD measurement of each precipitate (FIG. 3) And TEM photographs were taken (FIG. 4). From FIG. 3 and FIG. 4, it was confirmed that a rhodium-doped strontium titanate fine particle having a cubic perovskite structure can be obtained at least one hour after boiling.

The results of thermogravimetric-mass simultaneous analysis (using a thermogravimetric-mass simultaneous analyzer (using TG8121 manufactured by RIGAKU Co., Ltd.)) of the rhodium-doped strontium titanate fine particles according to Example 3 are shown in FIG. It is assumed that the rhodium-doped strontium titanate fine particles are in a water-containing state, since the elimination of the substance corresponding to the molecular weight 18 was observed along with the decrease. It is estimated that the lattice constant value (0.3905 nm) of known SrTiO ₃ is slightly increased.

(Example 4)
The amount of rhodium chloride (RhCl ₂ ) added was [Rh] / [Sr] = 0 (Example 4-1), 0.02 (Example 4-2), 0.03 (Example) in the reaction solution. 4-3) Same as Example 1 except that 0.05 (Example 4-4), 0.10 (Example 4-5), and 0.15 (Example 4-6) were used. Then, rhodium-doped strontium titanate fine particles were prepared. The results of photographing these XRD spectra and TEM images are shown in FIG. 5 and FIGS. 7A and 7B. First, it was confirmed from the X-ray diffraction pattern of FIG. 5 that a single phase perovskite structure is obtained up to a rhodium doping concentration of 5%, and that a different phase is generated at a rhodium doping concentration of 10% or more. Further, it was confirmed from the TEM photographs of FIGS. 7A and 7B that rhodium-doped strontium titanate fine particles having a cubic shape can be obtained at any doping concentration. Furthermore, the result of having calculated the lattice constant from the peak position of a XRD pattern is shown in FIG. The lattice constant gradually increased in proportion to the rhodium doping concentration, showed a maximum at about 7%, and then gradually decreased. Judging these things collectively, it can be judged that rhodium is properly incorporated into the lattice and solid-dissolved up to a rhodium doping concentration of about 7%.

  Furthermore, the result of measuring the limited field electron diffraction pattern is shown in FIG. 7C. From these results, it was confirmed that the exposed surface of the rhodium-doped strontium titanate fine particles according to the present synthesis method is the (100) surface.

  It was confirmed that the color tone of the synthesized product changed to yellow as the rhodium doping amount was increased. Therefore, when the diffuse reflection spectrum was measured, the absorption at 350 nm to 500 nm was increased as the rhodium doping amount increased (FIG. 8). The optical band gap calculated from these diffuse reflection spectra is 3.54 eV in the non-doped state, and the band gap narrows as the rhodium doping amount increases, and becomes 3.21 eV in the rhodium doping amount of 15%. Was confirmed (Figure 9). These results are experimental evidence to support that Rh is substituted and solidly dissolved in Ti sites properly as the amount of rhodium doping increases. Also, it is clear that the narrowing of the bandwidth can effectively absorb the wavelength of the visible part of sunlight.

(Composition analysis)
Inductively coupled plasma (ICP) for Rh-doped strontium titanate fine particles having a Rh concentration of 3% by mole and Rh-doped strontium titanate fine particles having a Rh concentration of 1% by mole in Example 4 The results are shown in Table 2. In the solid phase method, strontium carbonate (SrCO ₃ ), titanium dioxide (TiO ₂ ), and rhodium oxide (Rh ₂ O ₃ ) are mixed, subjected to calcination at 900 ° C. for 1 hour, and then ground and 1000 ° C. The main firing was performed for 10 hours and the mixture was crushed to obtain Rh-doped strontium titanate fine particles.
As shown in Table 2, it was confirmed that the rhodium concentration in the fine particles obtained by synthesis was approximately the same as the feed composition.

(Rhodium electron state evaluation)
In order to investigate the electronic state of rhodium contained in rhodium-doped strontium titanate prepared by this synthesis method, Rh valence measurement (Bruker Biospin Co., Ltd. EMX ESR apparatus) by electron spin resonance (Electoron Spin Resonance (ESR)) Figure 10 shows the results of using. Moreover, the result of having measured the ESR signal derived from Rh4 valence about the sample manufactured by the solid-phase method is shown in FIG. In the rhodium-doped strontium titanate synthesized by this synthesis method, a peak signal derived from tetravalent rhodium was not detected. Rhodium is known to be trivalent or tetravalent and stable, and the trivalent of rhodium is inert to ESR. From these results, it was suggested that rhodium exists in trivalent. The trivalent of rhodium is considered to contribute to the improvement of the photocatalytic ability, and the rhodium-doped strontium titanate according to the present synthesis method is expected to be a suitable raw material for the photocatalyst.

(Example 5)
Next, in order to verify the influence of pH, the pH is adjusted to pH 14.3 (Example 5-1), pH 13.5 (Example 5-2), pH 12 (Example 5-3), and the Rh concentration is [Rh]. Strontium titanate fine particles were produced in the same manner as in Example 1 except that / [Sr] = 0.
(Example 6)
In order to verify the effects of pH and reaction temperature, the reaction temperature is 90 ° C. (Example 6-1) or 80 ° C. (Example 6-2), and the Rh concentration is [Rh] / [Sr] = 0. Strontium titanate fine particles were produced in the same manner as in Example 1 except for the above.
(Example 7)
In order to verify the conditions of manufacture of the rhodium-containing strontium titanate whose shape was controlled, it was prepared in the same manner as Example 1 except that the reaction temperature was set to 90.degree.

(Comparative example 1)
In order to verify the conditions of manufacture of the rhodium-containing strontium titanate whose shape was controlled, it was prepared in the same manner as in Example 1 except that the reaction temperature was set to 77 ° C.

(Evaluation of reaction conditions and cube shape)
Table 3 shows the evaluation results of reaction temperature and pH condition, [Rh] / [Sr] value, and cube shape for the strontium titanate fine particles or rhodium-doped strontium titanate fine particles obtained in the above Examples and Comparative Examples. It is In Table 3, evaluation of cube shape is described by 4 steps of Excellent, Good, Passable, and Bad. For evaluation, in an electron microscope (TEM) photograph, a single isolated particle image is circumscribed by a rectangle that minimizes the area, and the area S _{0 of} the rectangle and the area S _{cube of the} particle image to S _cube / S ₀ It is performed by obtaining a value, and 0.9 <S _cube / S ₀ is Excellent, 0.85 <S _cube / S ₀ ≦ 0.9 Good, and 0.8 <S _cube / S ₀ ≦ 0.85 is Passable. , S _cube / S ₀ ≦ 0.8 is Bad.

  Whether or not the shape-controlled rhodium-containing strontium titanate was produced was mapped in FIG. 13 as the reaction temperature on the vertical axis and the [Rh] / [Sr] value in the reaction liquid on the horizontal axis. In FIG. 13, symbols of each plot correspond to evaluation of particle shape in Examples described later, and plots of ◎ are fine particles of excellent evaluation, plots of ○ are fine particles of Good evaluation, and plots of Δ are fine particles of Passable evaluation, The x plot shows fine particles of Bad evaluation.

  The method for producing oxide fine particles of the present invention can provide cubic oxide fine particles having a uniform particle system distribution at low temperature and low temperature, so that it can be used for devices using various metal oxide particles. is there. For example, it can be preferably used as a raw material for photocatalysts of a hydrogen generation photocatalyst system and an oxygen generation photocatalyst system. At the same time, it can be preferably used as a raw material of an electrode-constituting material (ohmic forming layer etc.) for electronic parts such as ceramic multilayer capacitors.

Claims (14)

A reaction liquid preparation step of preparing a reaction liquid in which a strontium raw material and a titanium raw material are added to an alkaline aqueous solution;
The reaction was heated to 80 ° C. or more under atmospheric pressure possess a reaction step of reacting the reaction liquid,
In the reaction liquid preparation step, the Rh raw material is added to the alkaline aqueous solution having a pH of 12 or more, or, the Rh raw material and V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga , Nb, Mo, Ru, Pd , in, Sb, Ta, W, Re, Ir, Pt, Bi, or cubic shape you preparing at least one of the reaction solution and the metal material is formed by the addition of La A method for producing strontium titanate fine particles having the   The method for producing strontium titanate fine particles having a cubic shape according to claim 1, wherein the titanium raw material contains a titanium oxide.   The method according to claim 2, wherein the titanium oxide is titanium dioxide.   The method for producing strontium titanate fine particles having a cubic shape according to claim 3, wherein the main component of the titanium dioxide is anatase type titanium dioxide. The strontium titanate having a cubic shape according to any one of claims 1 to 4, wherein the strontium raw material contains at least one of strontium acetate, nitrate, carbonate, chloride, sulfide and hydroxide. Method of producing microparticles.   The temperature at which the reaction liquid is reacted in the reaction step is 90 ° C. or more and the boiling point or less, The method for producing cubic strontium titanate fine particles according to any one of claims 1 to 5. The method for producing strontium titanate fine particles having a cubic shape according to any one of claims 1 to 6, wherein a pH of the reaction solution is 13.5 or more in the reaction step. The method for producing strontium titanate fine particles having a cubic shape according to any one of claims 1 to 7 , wherein the Rh raw material and the metal raw material in the reaction liquid are water-soluble raw materials. The total molar ratio of the Rh raw material and the metal raw material to the molar amount of the strontium raw material in the reaction solution is 0.15 or less, The cubic strontium titanate fine particles according to any one of claims 1 to 8 , Production method. The method for producing strontium titanate fine particles having a cubic shape according to any one of claims 1 to 9 , wherein Rh raw material is added to the aqueous alkali solution in the reaction liquid preparation step. Formula _{Sr (Ti 1-x (Rh} 1-y, M y) x) is represented by _{O 3,}
0 . 05 ≦ x ≦ 0.07 and y = 0 , M is V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Nb, Mo, Ru, Pd, In, Sb, Ta, W Cu-shaped rhodium-doped strontium titanate fine particles which are at least one metal element selected from the group consisting of Re, Ir, Pt, Bi and La. Lattice constant value, rhodium-doped strontium titanate fine particles of the cubic shape of claim 1 1 wherein the 0.3930nm the range above 0.3915Nm. Optical band gap is in the range from 3.21eV to 3.54eV, rhodium-doped strontium titanate fine particles of the cubic shape of claim 1 1, wherein. Average length of one side, claim 1 1 claims 1-3 rhodium doped strontium titanate fine particles of the cubic shape of any one claim is 30Nm～80nm.